1. Field of the Invention
This invention relates to an electronic component-mounting apparatus of a multi-function type for mounting electronic components supplied by using a pallet, on a circuit board.
2. Prior Art
Conventionally, an electronic component-mounting apparatus of this kind is known in which electronic components are directly fed to a main block thereof by bringing a pallet to a predetermined position in a pickup area of the main block, the pallet carrying thereon a single or a plurality of trays on which a lot of electronic components are juxtaposed (as disclosed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 3-257896). Such an electronic component-mounting apparatus includes an elevating mechanism for lifting and lowering pallets each carrying trays thereon to selectively guide the pallets to the level of a transfer path of the main block of the apparatus, a pallet guide device for drawing out the selected pallet from the elevating mechanism to the predetermined position in the pickup area along the transfer path, and a component-mounting device for picking up electronic components from the drawn-out pallet and mounting the same on a circuit board by using mounting heads thereof. Each pallet is lifted or lowered to the level of the transfer path by the elevating mechanism to be horizontally drawn out to the predetermined position in the pickup area by the pallet guide device.
The pallet guide device includes an engaging arm unit having an engaging arm rotatable to engage with a front edge of a pallet from above and a solenoid for actuating the engaging arm for engagement with and disengagement from the pallet, and a unit-moving device for moving the engaging arm unit forward and backward along the transfer path by using a motor as a drive source therefor. To draw out a pallet from the elevating mechanism, first the unit-moving device is driven to advance the engaging arm and the solenoid. When the engaging arm has reached the pallet, the engaging arm and the solenoid are stopped. Then, the solenoid is energized (or deenergized) to rotate the engaging arm to engage the same with the pallet. In this state, the engaging arm and the solenoid are moved backward to thereby draw out the pallet to the predetermined position in the pickup area. When a used pallet is returned to the elevating mechanism, the returning operation is carried out by completely reversing the above procedure.
The elevating mechanism and the pallet guide device are adjusted to operate at respective low speeds so as to prevent electronic components from leaving or jumping out of each component-holding groove in the tray. That is, each pallet is guided far more slowly than each mounting head carries out a sequence of operations required to pick up and mount an electronic component on the circuit board. When pallets are replaced, each mounting head has to wait until it is permitted to operate, resulting in an increase in tact time as a whole.
Further, in the case of the above-mentioned conventional electronic component-mounting apparatus, the pallet guide device is required to have two actuators (drive sources), i.e. a motor for the unit-moving device and a solenoid for the engaging arm unit, so that the conventional electronic component-mounting apparatus is complicated in construction. Moreover, the motor and the solenoid are driven in a manner interlocked with each other, which complicates the control of the apparatus.